The primary goal of the proposed research is to develop a new ultrasonic measurement technique which will allow accurate, precise, and convenient in vivo assessment of volumetric flow. Currently available techniques are largely qualitative for such measurements. The ultrasonic time-domain correlation technique has already been demonstrated to be an accurate and precise technique for the quantification of volumetric flow in phantoms. The theoretical foundation of the technique has been well described and a theoretical verification through computer simulation has been performed to evaluated all of the various system parameter effects on the estimation of flow velocity. Additionally, experimental verification has been carried out with a blood vessel phantom. The proposed research program is to continue to develop the ultrasonic time-domain correlation technique for application of volumetric blood flow in vivo. It is felt that a thorough and careful evaluation of this technique is essential in an animal model before a system can be pursued for human clinical validation.